Incorrect schema.org pricing markup.

[gavinballard]

We get a lot of Shopify stores using Timber install our app, JSON-LD for SEO. One of the first things people do after installing the app is check their structured data report using Google's Structured Data testing tool.

There's an issue with the way Timber outputs product price information by default that we've seen repeatedly cause merchants concern - the price item property is being returned formatted, which Google doesn't expect.

I'll raise a PR with a fix.